1. Field of the Invention
This invention relates to control apparatus for a carriage which is given with a propelling force and runs by its inertia, the apparatus being capable of accelerating or decelerating the carriage and more particularly control apparatus capable of applying an appropriate acceleration or deceleration corresponding to the kinetic energy of the carriage.
2. Description of the Prior Art
The control apparatus of the type described above is used in a conveyer system utilizing a linear induction motor, for example. In a linear induction motor, magnetic flux which varies with time is applied to a reaction plate and by the variation in the magnetic flux, a definite propelling force is created in the reaction plate. When the direction of the magnetic field is changed, a reverse propelling force can be produced. In this system, the reaction plate is secured to the carriage whereby the linear induction motor applies a forward propelling force or a reverse propelling force to the carriage for effecting start, acceleration, deceleration or stopping control of the carriage.
Where it is desired to further accelerate, or decelerate and stop a carriage running under inertia after acceleration with a linear motor, by using another linear motor, a problem arises as to how to apply to the carriage an appropriate acceleration force (forward propelling force) or deceleration force (reverse propelling force). More particularly, where it is desired to further accelerate a carriage running under inertia, it is necessary to apply an adequate additional propelling force corresponding to the mass and speed of the carriage. When the applied propelling force is not adequate, it would be impossible to accelerate the carriage to a desired speed. To decelerate or stop a carriage running under inertia, it is necessary to apply to the carriage an adaquate reverse propelling force corresponding to the mass and speed of the carriage. When the reverse propelling force thus applied is not adequate, not only will a severe impact be given to the carriage, but also there is a case in which it is impossible to decelerate the carriage to a desired speed. Furthermore in other cases, it is impossible to stop the carriage at a desired position. Where the applied reverse propelling force exceeds the inertia of the carriage, the carriage may jump in the opposite direction which is of course extremely dangerous.
To solve these problems, there has been proposed a control apparatus disclosed in Japanese Patent Application No. 26460/1979 (Laid Open Patent Specification No. 119616/1980). According to this prior art technique, the mass of the carriage is detected from its speed immediately after starting for controlling the braking force applied to the carriage based on the detected mass and speed thereof. According to this technique, however, it is not always possible to correctly detect the mass of the carriage due to the condition of the conveying road or path at the time of starting. For this reason, it has been impossible to apply an adequate braking force to the carriage.